The present invention relates to a heat exchanger in a simple structure which can be applied to a heat exchanger (EGR cooler) used in an exhaust gas recirculation apparatus in an automobile and other heat exchangers, in which a core body formed by bending a strip-shaped metal plate in a fanfold manner, and having flat first flow passages and second flow passages alternately in the thickness direction of the metal plate, each of the first flow passages of the core body being blocked by each tooth of a pair of comb-state members at both end positions.
A conventional EGR cooler is made of an assembly of a large number of flat tubes or a large number of plates, a large number of fins, a casing and a header, in which cooling water is made to communicate through the casing side and an exhaust gas is made to communicate inside each of the flat tubes or the like as proposed in the invention described in Japanese Patent Application Laid-Open No. 5-18634.
Another heat exchanger is proposed in which a core of the heat exchanger is formed by a strip-shaped metal plate bent in a fanfold manner and a pair of comb-state members, the outer periphery being fitted with a cylindrical casing, and a pair of headers are provided at openings on both ends in the longitudinal direction and ports for cooling water at both ends of the casing in the longitudinal direction as in the invention described in WO 2004/065876 A1.
In the former heat exchanger such as the EGR cooler, the number of parts is large, which makes assembling cumbersome and increases the number of brazing portions on the parts, and there is a problem that a leakage tends to occur at the brazing portion.
In the latter heat exchanger, comb teeth of the comb-state member are arranged at every other of the large number of flat groove-state portions in a core body formed in the fanfold state, and the groove bottom and the tip end of the comb tooth are bonded. And the casing is fitted with the outer periphery of the core. In this type of heat exchanger, there is a problem that a gap tends to occur at a brazed portion between the root of each comb tooth and the side face of the core body as well as between the tip end of each comb tooth and each groove bottom, from which leakage of a fluid easily occurs. Along with that, a crack is easily generated at a brazed portion particularly at the root portion of each comb tooth by a heat stress or the like due to use of the heat exchanger.
The present invention has an object to provide a heat exchanger in which the number of parts is small, assembling is easy, leakage does not occur, and reliability in a brazed portion is high.